A conventional swash plate compressor comprises a piston reciprocally moved by the rotation of a swash plate fixed to a drive shaft. The swash plate is a rigid plate or disc, typically made of low-carbon steel or a high silicon-zinc-copper alloy, which is affixed to a drive shaft. The drive shaft runs through the center of the swash plate at an angle such that the swash plate is not mounted perpendicularly to the drive shaft. This mounting angle causes the swash plate to ‘wobble’ as the drive shaft rotates. This wobble is used to drive one or more pistons.
The swash plate and a contact portion of a piston are engaged through a pair of hemispherical shoes, which are typically made of steel or other metals or alloys. Each of the shoes has a hemispherical surface which engages with the contact surface of the piston, and a flattened portion to engage the swash plate. The shoes engage the swash plate, and, as the swash plate rotates, the shoes are forced to move by the motion of the swash plate as it rotates about its axis. As the shoes move, they force the piston to move between the two ends of a cylinder.
A significant problem in swash plate compressors is maintaining sufficient lubrication between the swash plate and the shoes. The slidability and the seizure resistance between the flattened surface of the shoe and the surface of the swash plate are important in order to assure the operability and the durability of the compressor as a whole.
To create sufficient lubrication between the swash plate and the shoes, the swash plate is typically plated with tin (Sn) or molybdenum disulfide (MoS2), both of which exhibit excellent lubrication properties. Alternatively, a thermally-applied solid lubricant, such as a leaded tin-bronze coating may be used. Thus, a soft-surface treatment layer having a lubricity is produced. Other attempts to provide lubricity between the swash plate and shoes have been primarily directed to applying lubricating coatings to the swash plate.
However, there are manufacturing expenses involved in applying a lubricating coating or plating to a swash plate. Applying the tin or MoS2 plating is a complex process, and applying the tin-bronze coating uses an expensive thermal spray process. Thus, it would be advantageous if more cost-effective method or product for maintaining lubricity between the shoes of a compressor and a swash plate could be used, while maintaining the level of performance of existing swash plate compressors.